SYNOVIAL METAPLASIA OF THE SKIN

We present two female patients, aged 15 and 45 years, with synovial me taplasia of the skin. Both lesions, localized in the knee and hand res pectively, arose after preceding local trauma. Case 1 had intradermal irregular cystic spaces in the adjacent myxoid stroma of which large p olygonal eosinophilic cells were found. In contrast, case 2 was charac terized by a longitudinal space within the lower dermis and subcutis w hich was lined by a membrane similar to hyperplastic synovium. The cel ls of the membrane showed an eosinophilic spindle shaped cytoplasm wit h processes towards the lumen. In both cases the eosinophilic cells, s trongly suggestive of fibroblasts, showed staining for vimentin only, whereas no reactivity could be obtained with antibodies to actin, desm in, S-100 protein, Factor VIII related antigen, cytokeratin, epithelia l membrane antigen, carcinoembryonic antigen and CD 68. The absence of CD 68 positivity differs from that seen in normal and hyperplastic sy novium. Delayed wound healing around a nidus seems the most likely cau se of the change.